Vulcanization accelerator



Patented July 25, 1939 UNITEDSTATES PATENT OFFICE VULCANIZATION ACCELERATOR Marion W. Harman, Nitro,'W. Va.,' assignor to Monsanto Chemical Company, St. Louis, a corporation of. Delaware No Drawing. Application May 26, 1936,

Serial No. 81,911

25 Claims.

The present invention relates to new vulcanization accelerators, to a process of vulcanizing rubber and tothe vulcanized rubber products obtained with the aid of the said new compounds.

5 32 The new and preferred-class of rubber Vulcan-' ization accelerators comprise the products formed by reacting an amine with a cyan-thio-formaromatic amide. The cyan-thio-form-aromatic amides -,may be assigned the, formula of "10: R.NH.CS.CN where R is an aromatic radical, and

may be prepared by the method of Arnold Reissert and Kurt Bruggemann, Berichte der Deutschen Chemischen Gesellschaft, 57, 981-989 (1924) by reacting an aromatic mustard oil with an alkali metal cyanide, after which the solution so formed is acidified. The materials of the present invention may be produced by reacting a cyan-thio-form-aromatic amide as described above with an amine and preferably an amine 2' having a high dissociation constant, and are believed to possess the structural formula of I where R is an aromatic'radical and R is an amine and preferably an amine having a high dissociation constant.

While the compounds of the present invention possess accelerating action when employed alone as the sole organic vulcanization accelerator, they are'found to possess surprising activating action when employed in conjunction with thiazole ac celerators, and are preferably employed in conjunction therewith. e

As specific examples-of -the present invention are" the diphenyl guanidine, di ortho tolyl guanidine, piperidine, ethylene diamine, cyclohexyla'mine,ethanolamine, di-n-butyl amine, phenyl biguanide, diethyl amine and analogous salts of 40 1 cyan thio formanilide, cyan-thio-form-alphanaphthalide, cyan-thio-ortho-toluidide, cyanthio-para-toluidide, cyan-thio-meta-xylidide and their analogues and equivalents.

Example I 67.5 parts by welght of phenyl mustard oil (onehalf a molecular proportion) were dissolved in a convenient amount of an organic solvent, for example 200 parts by weight of ethyl alcohol, and

25 parts by weight of sodium cyanide dissolved in water, for example 360 parts by weight thereof, are added thereto at room temperature with vigorous agitation. On diluting with water and acidifying with an acid as for example hydroufchloric acid, the precipitate which formed was separated and purified by redissolving' in a dilute aqueous sodium carbonate solution and reprecipitating with hydrochloric acid.

The product so formed after washing with water and drying,

melted at 80-81 C.

product so formed comprising cyan-thio-formanilide (0.1 molecular proportion) were placed in a suitable reactor and parts by weight of cyclohexylamine (0.1 molecular proportion) added thereto, whereupon an exothermic place forming first" a viscous liquid which later' reaction took set to .a. solid. It isbelieved the reaction takes place the/following manner:

HgNCtHu As stated above the resulting product, when employed alone, possesses accelerating properties,

but when employed in conjunction accelerators, 'it is found to possess surprising;

with thiazole activatingproperties. The following stocks were compounded:

Stock A Stock B Pale crepe rubber Zinc oxide r Sulfur Stearic acid Dibenzothiazyl-thiol-dlmethylurea Cyclohexylamine oyau-thio-formamlld The rubber stocks so compounded were vulcanized and the following tensile and modulus results obtained on the cured rubber products:

From the-data-set forth in Table I it is shown that the preferred'materials, for example cyclohexylamine cyanthio-formanilide,

is an exceptionally strong activator when employed in conjunction with thiazole accelerators.

16.2 parts by weight of the 5 Example II Substantially equi-molecular proportions of diphenyl guanidine and cyan-thio-formanilide were heated in the presence of alcohol as a solvent and the product so obtained, after the elimination of the solvent, incorporated in a rubber stock comprising:

Parts Pale crepe rubber 100 Zinc oxide 5 Sulfur 3 Stearic acid 1 Dibenzothiazyl-thiol-dimethylurea 0. 6 Diphenyl guanidine cyan-thio-formanilide 0. 1

The compounded rubber stock was vulcanized with the following result:

Table II Modulus of elasticity Cure in lbs/infl at elongatlms Tensile at Ult.

break in e1on2.,

' 7 Min Pounds lbs/1n. percent Utes steam 500% 700% pressure 7 Example III Substantially equi-molecular proportions of piperidine and cyan-thio-formanilide were reacted in a manner analogous to that employed in Example I. The dark solid so obtained was milled into a rubber stock comprising Parts Pale crepe rubber Zinc oxide 5 Sulfur 3 Stearic acid 1 Dibenzothiazyl-thiol-dimethylurea 0.6 Piperidine cyan-thio-formanilide 0.1

The compounded stock was cured and the results obtained as given in Table III.

Table III Modulus of elasticity Cure in lbs/in. at elongatmns Tensile at Ult.

brealr in elongl, Min Pounds lbs/m. percent utes steam 500% 700% pressure Example IV Substantially two molecular proportions of cyan-thio-formanilide and substantially one molecular proportion of ethylene diamine were reacted in a manner analogous to that employed in Example I. The solid product so obtained was milled in a rubber stock comprising Parts Pale crepe rubber 100 Zinc oxide 5 Sulfur 3 Ste-aric acid 1 Dibenzothiazylthiol-dimethy1urea V 0.6 Ethylene diamine cyan-thio-formanilide--- 0.1

The tensile and modulus characteristics obtained on the cured rubber product follow in Table IV:

Table IV Modulus of elasticity Cure in lbs/in. at elongatmnsOf Tensile at Ult.

break in elong,

' 2 Min Pgundsr 5007 7007 lbs/1n. percent S 83.111 utes pressure 0 0 Example V Substantially equi-molecular proportions of cyan-thio-forrnanilide and ethanolamine were reacted in a manner analogous to that employed in Example I. The viscous liquid so obtained was milled in a rubber stock comprising Parts Pale crepe rubber 100 Zinc oxide 5 Sulfur 3 Stearic acid 1 Dibenzothiazyl-thiol-dimethylurea 0.6 Ethanolamine cyan-thio-formanilide 0.1

The test results on the vulcanized rubberprod- Substantially equi-molecular proportions of di ortho tolyl guanidine and cyan-thio-formanilide were reacted in the presence of a convenient solvent, for example ethyl alcohol, in a manner analogous to that employed in Example II. The viscous liquid so obtained was milled into a rubber stock comprising i Parts Pale crepe rubber 100 Zinc oxide 5 Sulfur 3 Stearic acid ii 1 Dibenzothiazyl-thiol-dimethylurea 0.6

Di ortho tolyl guanidine cyan-thio-formanilide- 0.1

The tensile and modulus data obtained on the vulcanized rubber product are given in Table VI.

Table VI Modulus of elasticity Cure in lbs.ln. at elongatlms Tensile at Ult.

break in elongn, Min Pounds lbs/m. percent utes steam 500% 700% pressure Example VII Substantially equimolecular proportions of di-n-butyl amine and cyan-thio-formanilide were reacted in a manner analogous to that employed in the preparation of Example I. The yellow solid so obtained was incorporated in the usual manner into a rubber stock comprising Parts Pale crepe rubber 100 Zinc oxide; 5 Sulfur s Stearic acid e 1 Dibenzothiazyl-thiol-dimethylurea 0.6 Di-n-butyl amine cyan-thio-formanilide 0.1

Q'Ihe tensile and modulus data on the vulcanized rubber product are given in Table VII.

cyan-thio-form alpha-naphthalide and cyclohexylamine were reacted in a manner analogous .to that employed in Example I. The resinous solid obtained in the manner described was milled in a rubber stock comprising 7 Parts Pale crepe rubber 100 Zinc oxide 5 slllflll V 3 Stearic acid 1 Dibenzothiazyl-thiol-dimethylurea 0.6 Cyclohexylamine cyan thio form alpha naphthalide 0.1

The tensile and modulus dataon the vulcanized rubber product are given in Table VIII.

Table VIII Modulus of elasticity Cure in lbs/in. at elongatmns Tensile at Ult.

break in elong., Min Pounds lbs/in. percent utes steam 500% 700% pressure As further specific embodiments of the present invention, but not to be understood as limitative of the scope thereof, the following stocks were compounded comprising Stock Stock Stock Stock A B C D Parts Parts Parts Parts Pale crepe rubber. 100 100 100 Zinc oxide 5 5 5 uliur 3 3 3 3 Stearic acid 0. 5 0. 5 0. 5 0.5 Mercaptobenzothiazole 0. 75 0. 075 Benzotbiazyl-thio-benzoate 0. 75 0. 75 Cyclohexylamine cyan thio iormanilide 0. 0. 10

The stocks so compounded were vulcanized and the cured rubber product found on testing to possess the following modulus and tensile characteristics: 1

Table IX Modulus of elasticity in lbs/in) at elongations of Tensile Um Stock at break elongv Time Poundq in lbs/in! Percent minsteam 500% 700% utes pressure As is shown from the data hereinbefore set forth the new and preferred class of compounds are particularly strong activators for thiazole accelerators. The new and preferred class of compounds may conveniently be employed With other thiazole accelerators than those specifically set forth above. Thus, they may be employed in conjunction with dibenzothiazyl disulfide, mercaptonaphthathiazole, mercaptotolylthiazole, dinitrophenyl-benzothiazyl-sulfide and analogues and equivalents thereof.

This invention is not restricted to the use of the particular compounds given in the specification as specific examples, nor'is it restricted to the use of the preferred class of compounds in the particular rubber mixes hereinbefore described. The invention is limited solely by the claims attached hereto as part of the present specification.

What is claimed is:

1. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a thiazole accelerator and in addition thereto a reaction product of substantially one molecular proportion of a cyan-thio-form-aromatic amide and an equivalent amount of an amine having a dissociation constant at least equal to that of ethanol amine, said reaction being effected without the addition of heat.

2. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a thiazole accelerator and in addition thereto an amine salt of a cyamthio-form-aromatic amide, said amine of said salt having a dissociation constant at least equal to that of ethanol amine.

3; The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a mercaptoaryl-thiazole accelerator and in addition thereto an amine salt of a cyan-thioform-aromatic amide, said amine of said salt having a dissociation constant at least equal to that of ethanol amine.

4. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a mercaptoaryl-thiazole accelerator and in addition thereto an amine salt of a cyan-thicformanilide, said amine of said salt having a dissociation constant at least equal to that of ethanol amine.

5. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a mercaptobenzo-thiazole accelerator and in addition thereto an amine salt of cyan-thioformanilide, said amine of said salt having a dissociation constant at least equal to that of ethanol amine.

6. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of an amine salt of a cyan-thio-form-aromatic amide, said amine of said salt having a dissociation constant at least equal to that of ethanol amine.

'7. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of an amine salt of a cyan-thio-formanilide, said amine of said salt having a dissociation constant at least equal to that of ethanol amine.

8. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of dibenzothiazyl-thiol-dimethyl urea and in addition thereto cyclohexylamine cyan-thicformanilide.

9. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of dibenzothiazyl-thiol-dimethyl urea and in addition thereto ethanolamine cyanthioformanilide.

10. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of dibenzothiazyl-thiol-dimethyl urea and in addition thereto diphenylguanidine cyan-thioformanilide.

11. The vulcanized rubber product produced by heating rubber and sulfur in the presence ofa thiazole accelerator and in addition thereto an amine salt of a cyan-thio-form-aromatic amide, said amine of said salt having a dissociation constant at least equal to that of ethanol amine.

12. The vulcanized rubber product produced by heating rubber and sulfur in the presence of a mercaptoarylthiazole accelerator and inaddition thereto an amine salt of a cyan-thio-formaromatic amide, said amine of said salt having a dissociation constant at least equal to that of ethanol amine. 1

13. The vulcanized rubber product produced by heating rubber and sulfur in the presence of a mercaptoarylthiazole accelerator and in addition thereto an amine salt of a cyan-thio-formanilide,

said amine of said salt having a dissociation constant at least equal to that of ethanol amine.

14. The vulcanized rubber product produced by heating rubber and sulfur in the presence of a mercaptobenzothiazole accelerator and in addition thereto an amine salt of a cyan-thio-formanilide, said amine of said salt having a dissociation constant at least equal to that of ethanol 15. The vulcanized rubber product produced by heating rubber and sulfur in the presence of an amine salt of a cyan-thio-form-aromatic amide, said amine of said salt having a dissociation constant at least equal to that of ethanol amine.

16. The vulcanized rubber product produced by heating rubber and sulfur in the presence of an amine salt of a cyan-thio-formanilide, said amine of said salt having a dissociation constant at least equal to that of ethanol amine.

17. The vulcanized rubber product produced by heating rubber and sulfur in the presence of dibenzothiazyl-thio1-dimethyl urea and in addition thereto cyclohexylamine cyan-thio-formanilide.

18. The vulcanized rubber product produced by heating rubber and sulfur in the presence of dibenzothiazyl-thiol-dimethyl urea and in addition thereto ethanolamine cyan-thio-formanilide.

19. The vulcanized rubber product produced by heating rubber and sulfur in the presence of dibenzothiazyl-thiol-dimethyl urea and in addition thereto diphenyl guanidine cyan-thio-formanilide.

20. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of cyclohexylamine cyan-thio-formanilide.

21. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of ethanolamine cyan-thio-formanilide.

22. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of diphenylguanidine cyan-thio-formanilide.

23. The vulcanized rubber product produced by heating rubber and sulfur in the presence of cyclohexylamine cyan-thio-formanilide.

24. The vulcanized rubber product produced by heating rubber and sulfur in the presence of ethanol amine cyan-thio-formanilide.

25. The vulcanized rubber product produced by heating rubber and sulfur in the presence of diphenyl guanidine cyan-thio-formanilide.

MARION W. HARMAN. 

